PECULIARITIES OF METHANE CLATHRATE HYDRATE FORMATION AND SOLID-STATE DEFORMATION, INCLUDING POSSIBLE SUPERHEATING OF WATER ICE

Slow, constant-volume heating of water ice plus methane gas mixtures f orms methane clathrate hydrate by a progressive reaction that occurs a t the nascent ice/liquid water interface. As this reaction proceeds, t he rate of melting of metastable water ice may be suppressed to allow short-lived superheating of ice to at least 276 kelvin. Plastic flow p roperties measured on clathrate test specimens are significantly diffe rent from those of water ice; under nonhydrostatic stress, methane cla thrate undergoes extensive strain hardening and a process of solid-sta te disproportionation or exsolution at conditions well within its conv entional hydrostatic stability field.